Radiopaque materials utilized today are generally of two types, viz, barium sulfate preparations and preparations containing iodinated organic compounds. The first of these types of preparations, i.e. preparations containing barium sulfate, suffer a number of disadvantages most of which are related to difficulty in obtaining a stable, high density, homogeneous suspension of the extremely insoluble barium sulfate and causing such suspensions to adhere to the intestinal mucosa. Even if such problems were to be overcome by the discovery of an ideal vehicle for barium sulfate, the resulting preparations would still not be amenable to the use of high energy X-rays. It is recognized that the use of high energy X-rays results in a decrease in the radiation dose absorbed by the body relative to the amount of information-bearing X-rays which reach the radiation detector system. It is also recognized in the art of radiopaque preparations that, as the energy level of X-rays utilized increases above the K-absorption edge of barium, the relative absorption of barium and its salts decreases. The same is true for the organic iodine preparations.
The fact that barium sulfate and the iodine preparations are optimally suited for use with medium energy X-rays and are inefficient in absorbing high energy X-rays whose energy significantly exceeds their K-absorption edge is of critical importance to the patient. The type of studies contemplated with such preparations, particularly the barium sulfate preparations, require the use of not only a large quantity of the preparation itself but also, because of their X-ray absorption properties, a very large dose of radiation. This is unfortunate but necessary to obtain satisfactory diagnostic information, e.g. when conducting a gastrointestinal tract study. It has been long established that the higher the energy level of radiation passing through the human body the less energy is absorbed thereby. Therefore, it is readily apparent that X-ray contrast preparations which are optimally suited for use with high energy X-rays would be highly advantageous in comparison with the barium sulfate and iodinated preparations in terms of the amount of radiation absorbed by the patient. Such preparations are provided by the present invention.